In air conditioned buildings an attempt is made to maintain the interior temperature at the most comfortable level, e.g., at 22.degree. C. (72.degree. F.). The required cooling effort, that is, the amount of heat that must be withdrawn from the interior of the building is a function of both the outside temperature, any heat generated within the building (such as from machinery located therein), and heat radiated into the building by the sunlight (hereinafter sometimes referred to as "solar heat gain"). Depending on the building construction, and particularly the relative proportion between solid walls and glass walls or windows, between about 20-40% of the cooling effort is to offset the solar heat gain. Attempts have been made to reduce the solar heat gain as by employing heat absorbing glass, light reflecting glass, etc. However, these attempts are of limited effectiveness.
In modern office buildings it is generally assumed that one ton of air conditioning is required for every 250-350 square feet of floor area. For a moderate size building of 15 floors with a typical floor area of 10,000 square feet, between about 430-600 tons of air conditioning is required. If the solar heat gain could be eliminated or at least substantially reduced, so that the overall air conditioning load could be reduced by about 30%, for example, 150 tons of air conditioning could be deleted from such a building. At an average air conditioning plant cost of about $1,500 per ton initial plant savings would amount to approximately $225,000. More importantly, the reduction in the size of the air conditioning plant substantially reduces the energy requirements which result in correspondingly lower running costs and an energy conservation. With today's increasing difficulty in satisfying a modern society's energy requirement, coupled with the ever increasing demand for greater comfort, such an energy saving is truly significant. Moreover, the reduced air conditioning load which must be carried by the air conditioning system of the building permits the installation of smaller air conditioning ducts, which in turn saves building space by lowering the required floor height to thereby reduce the overall building costs.